Method of reducing iron ore.



' G. GRNDAL.

METHOD 0F BEDUGINGNIRON ORE.

APLIGATIQN FILED NOV. 4, ,1909.

Patented July 146 1912.

2 SHBMSTSHBBT'L /17- TOR NEYs G. GR-NDAL.

l METHOD 0F REDUCING IRON ORE.

APPLICATION FILED NOV. 4, 19,09.

1,033,051, v Pavuented 1111511611912;

2 SHEETS-SHEET 2.

HYVENTOR GUSTAF Gacivniii.,l or DJURS'HO'LM, SWEDEN.

METHOD OF REDUCING IRON ORE.

To au iv/L'om' it may concern:

Be it known that I, GUSTAF GRNDAL', a subject of the King of Sweden, and resident of Djursholm, Sweden, have invented a certainnew and useful Improved Methodof Reducing Iron Ore, of which. the following is a specification.

If a suitable mixture of iron ore and charcoal, coke or other suitable solid carbona'ceous matter hereafter referred to as carbon isl heated to the necessary degree the iron is reduced under certain circumstances, completely and always more efficient-ly, the more finely divided or intimately mixed the raw materials aie. According to my invention the heating is effected by a gas or gas mixture of the necessary temperature led directly through or over the ore-carbon mixturein a suitable furnace during a period of such length that the whole of the iron in t-heore will be reduced to the metallic state` the reduced product being then re moved from the furnace and allowed to cool, protected against oxidizing. A suitable proportion of carbon and oreinthe said orecarbon mixture has been found to be about Q0 1per cent.- of carbon in proportion to the percentage of iron of the ore, provided the gas orvgas mixture is such a one as-to be indifferent tothe process of reduction and only acts as ai carrier of heat. A reducing gas or gas mixture may of course also be used. 'ven an oxidizing gas or gas mixture might' be used, but then the percentage of carbon in the ore-carbon mixtureA niustbe increased.

For obtaining a continuous process I em- `loy an inclined cylindrical furnace mounted and. kept rotating in the usual manner. One end of the furnace communicates with a device for .charging the ore-'carbon mixture and its other end communicateson the onehand with a discharge for the reduced product and on the other hand with arecuperator; from which the heated gas or gas mixture comes and sweeps through the furnace. Tliegases produced during the reduction in the furnace consisting'of carbonio oxid and carbonio acid as w'ell as the gas or gas mixture used for heating are led from the charging end ofthe furnace tof a 'fanll or blower or simil'a'r apparat-us and they-'are' forced back to the recuperator and through it and afte being heated to a suitable temperature say 800o C. again through the fur.

Specification of Iietters Patent. Y

Patented Jul-y 16,1912.

Appnctionraied November 4, 1909. serial No. 526,213.A

nace. Here they are mixed with the gases generated during the continued reduction' and forced back to the recuperatorv and through it(` and so on in a continual ciiculation. The excess of gases arising fromthe addition of thegases generated during the continuous process of reduction and Awhich is notneeded for the transmission of heat,V

is led away and used for 'heat-ing the recuper.i ator into which it is led and where the combustible part is burned. The heating ofthe i'ecuperator, however, is principally edected by a particular firing, forinstance by means of generator gas.- A portion of the just mentioned excess of gas may be' burned in a drying apparatus and used for drying and preheating the ore-carbon 'mixture before feeding it into the furnace as said mixture ought to be dry. f

On the accompanying draw-ing an arrangement of furnace for carrying out the newv process in a continuous manner is shown but as-an example only. 'y h Figure 1 represents a 'longitudinal' section lof the arrangementI and Fig. 2 lis a yplan III- III of Fig. 1 and Fig. 4 isa section on line llf-IV of Fig. 1. Fig. 5is a plan view of part of the apparatus' showing a modified form and Fig. 6 is a part of Fig. 1 showing another modified form.

1 indicates the rotating furnace supported and rotated in a known manner. The charging end of the furnace extends into a tower, the upper part of said tower being a drying apparatus 2 for the ore-carbon mixture charged into it.

indicates a screw conveyer for feeding the material to a pipe t leading to the furnace. The other end ofthe furnace extends into a channel 5 made of brick work and communicating with the recuperator 6. The latter may be of any ordinary construction.

7 indicates a conduit from a gas generator'7 not shown, and 8 a conduit for the combustion air under pressure.

9 indicates a fan or blower, its inletl communicating through a vflue l0 in the tower with the gasoutlet from the. furrace. T he pressure conduit 11 from the blower branches and fone branch 18 enters into the inletport 1.2 of the recuperator 6 while the other branch 14; opens into th gas conduit 7 from `the gas generator andv is provided with a branchingvoif from the pressure conduit ll and opening into .a combustion deviceof any suitable construction in the lower part of Vthe drying.V apparatus 2. v17 indicates the chimney belonging thereto. v

The Ypressure conduit 1l is provided with a dust collector or filtering means of any suitable kind, notf shown, for preventing dust from entering into the recuperator.,

'18.indicates an voutletport arranged in the channel 5 for the reduced product and 19 a truck placed under it on atracl.v Said truck being of a .known construction andof such a i -form that-a simple luting is enough for effectingl the tightening' .between the truck andthe outlet port Whenrequired."

ment -of furnace describedv above for this purpose.

In this gure21 indicates a conduit branchin oft from the conduit 7 for the gas from t e generator and opening into the conduitl from the blower 9.` v22 indicates a regulating valve in the conduit 21,

means of which thefeed ofgeneratorgas may be regulated.

Fig. 6 represents anlarrangementof furnace forV feeding air to the heat carrying gas mixture which .takes vplace throughthe pipe 23. 24 indicates a regulating'valvein this pipe. Saidpipe and valve' are also shown in Fig. 5. 1 l

For carrying out the'process the furnace and recuperator are heated by' gas firing or in any other suitable Way and after their being sufficiently heated the orecarbon mixture is charged intovthel furnace and the blower is set Working, the process afterward continuing uninterruptedly in the manner clearly seen from the foregoing desgription. lWhen using an indifferent gas or gas mix ture as heat carrier a mixture of ore and carbon suitable for the process is obtained if the carbon amounts to about 20. per cent. of the percentage 'of iron in the ore. reducing gas mixture is used the composition of the ore-carbon mixture may be the same or the percentage ofsolid carbon may be diminished, but When using an oxidizing gas mixture the percent-age of solid carbon must be increased.

Above it has been spoken of a recuperator for heating the gas and such an apparatus has been shown on the drawing, but any other suitable heating device may be employed, and the combustion material need not necessarily be generator' gas. The heating may even be effected by electricity if de-` sired Without departing from the invent-ion.

I claim l. Method of reducing ironore by mixing the ore in a ne state of division with finely 20. indicates V- the chimney' of the .recuperl the i divided solid carbon and heating the mixture in a suitable furnace directly bymeans of the vgases developed by the reduction of theore. in the furnace, Which are forced through asuitable heating apparatus and reheated and forced in unaltered condition through the furnace and brought in contact:

With the ore-carbon mixture.

2; Method of reducing iron ore by mixing Athe ore in a fine state of division With finely divided solid carbon andheating the mix# ture in asuitable furnace `directly by means of the gases developed by the reduction'of the ore in the furnace,- Which are'forced' through a suitable heating apparat-us and reheated together with othergases and furnace and brought in contact With the ore'- carbon mixture.

` 3. Method of reducing iron ore by mixing the ore in a fine state of ldivision With finely ydivided solid carbon and heating the mix-vv ture in a suitable furnace directly by means of the gases `developed by the reduction of the ore in the furnace, Which are forced through a suitable heating apparatus and reheated and forced through-the furnace and brought in contact With the ore-carbon mixture, a portion of theexcess gases from the 'furnace 4being used to heat the circulating part of the gas mixture that passes through the heating apparatus and the furnace in a continual circulation.

4. Method of reducing iron ore by mixing the orein aline state of division with finely cess gases fromthe furnace 4.being employed' to heat the part of the gas mixture that passes through the heating apparatus and the' furnace in a continual circulation.

5. Method of reducing iron ore by mixing the'ore in a fine state of division With finely divided solid carbon and heating the mixture in a suitable furnace directly by means of the gases developed by the reduction of thel ore in the furnace, Which are forced through a suitable heating apparatus and reheated and forced through the furnace and broughtv in contact With the 4ore-carbon mixture, the excess gases from the furnace being employed to heat the part of the gas mixture'that passes through the Aheating apparatus and the furnace in a continual circulation, and also for-preheating the orecarbon mixture.

6. Method of reducing iron ore by mixing the ore in a line state of division With nely divided solid carbon and heating the mixture .forced in unaltered condition through the i las in a suitable furnace directly by Iheans ofthe gases developed by the reduction of the ore in the furnace, which are forced through a suitable heating apparatus and reheated together with other gases and forced through the furnace and brought in contact with the ore-carbon mixture, the excess gases from the furnace bein-g employed to heat the part of the gas mixturethat passes .through the 10 heating apparatus and the furnace in a oontinual circulation, and'also for preheating the ore-carbonlmixture.

In testimony whereof I have signed my name to this specication, in the presence of two subscribing witnesses.

. y GUSTAF GRNDAL.

Witnesses: i' f 1 ANNA SDERSTRM, C. BRODIN. 

